4.1. Symmetry/Asymmetry, Elliptical Fourier analysis (EFA) and Modularity perspectives in skull development
Cranial asymmetry sheds light on developmental process disruptions in species (Elliot, 2010) and pathological conditions involving the skull (Elliot, 2006), it emphasizes relationship between structurally or functionally interacting elements (Benitez et al., 2020). DA and asymmetry studies are relatively scarce or non-existent in literature for small African pangolins, FA is the bilateral asymmetry that represents minute random developmental differences between a right and its left side (Benitez et al., 2020). Klingenberg (2008) showed that within the concept of geometric morphometrics studies of asymmetry can be combined with other morphological issues – modularity and integration. While modularity refers to the covariance among morphological structures that originates in independent developmental processes (so-called modules), integration; a counterpart to modularity, is a measure of the interconnection among parts in order to function as a whole unit (Klingenberg, 2008). Modules may be defined with respect to genetic, developmental, functional or evolutionary context as being currently interrogated. A low covariance (representing magnitude of interaction among modules) is expected if two modulating units possess a weak boundary suggestive of relative independence (Urbanova et al., 2014); the converse is also true. Elliptical Fourier analysis is fundamentally a mathematical application in the derivation of biological closed shape outlines evaluations and valued for its automatization of image analysis irrespective of morphological complexity for less experienced users (Schmittbul et al., 2000). The method demonstrates precise individual variations introducing scientific perspectives in characterization of closed shapes such as the foramen magnum (Samuel et al., 2017; Daegling and Jungers, 2000) in making useful inferences on developmental instability in a population of samples.